Toshiro Sakae

Changes in Bovine Dentin Mineral with Sodium Hypochlorite Treatment

Dentin powders from bovine incisors were treated with 10% NaClO solution. Differential thermal analysis (DTA) indicated the removal of organic material from the dentin sample following the treatment, since the exothermic reaction at 320°C had disappeared. X-ray diffraction studies revealed a change in the crystallinity of the dentin crystals and the formation of calcite after the treatment. Infrared absorption analysis showed that the band due to carbonate ions was weakened after the treatment, while atomic absorption spectroscopic analysis showed that magnesium ions had been dissolved from the dentin sample. The a-axis lengths of treated and heated dentin samples differed from those of untreated and heated samples. Whitlockite was always found in the untreated/heated samples, whereas it was absent in the treated/heated samples. The unit cell dimensions of the whitlockite indicated the partial substitution of magnesium for calcium. Magnesium ions seemed to be more effective than carbonate ions in forming whitlockite. These results showed that some magnesium and carbonate ions were removed from the dentin crystal structure upon NaClO treatment, while at the same time organic materials were removed from the dentin sample. It was suggested that crystals in the NaClO-treated dentin were similar to enamel crystals from a crystallographic viewpoint.

SCANNING ELECTRON MICROSCOPIC AND X RAY MICRODIFFRACTOMETERIC STUDIES ON SIALOLITH‐CRYSTALS IN HUMAN SUBMANDIBULAR GLANDS

The crsytalline structures of 18 submandibular gland calculi were studied by radiomicrography, scanning electron microscope, and X ray microdiffractometeric techniques. The following observations were made by SEM: Granular or globular structure was seen on the surface of all cases and pyramidal crystal in one case. In the inside, all showed lamellar pattern with amorphous nucleus in the center, and granular, plate‐like and rhombohedral structures were also observed. X‐ray microdiffractometeric analyses: Apatite was frequently observed in both outside and inside of the calculi. Whitlockite was next frequently detected and was seen more often in the inisde. Brushite and weddellite were noted in the outside of calculi in one case each. Thus, it is suggested that brushite and weddellite were present in the front portion of calculus formation and then transformed into the more stable form e.g. apatite.

Bone Formation Induced by Several Carbonate- and Fluoride-Containing Apatite Implanted in Dog Mandible

Synthetic hydroxyapatite (HAP), carbonate-apatite (CHA) and car bon te-fluoride-apatite (CFA) were implanted into dog mandible bone for 2, 3, 4, 5 and 6 weeks. The che mical composition and crystallographic properties of the synthetic apatites were examined using FT-IR, TG-DTA, AAS and X-ray diffraction. The comparative resorption in vivo for the experimental period was in the order: CHA >> CFA > HAP. CHA formed new bone com parable with the shamcontrol, and CFA induced fast bone-remodeling and newly formed Haversian s y tem. The results confirmed that CHA are potential bone-grafting materials and als o showed that CFA, compared to CHA or HAP materials, accelerate bone formation. Introduction Carbonateand/or fluoride-containing calcium hydroxyapatite are conside red as possible bone graft materials [1-3]. In vitro and in vivo studies showed that fluoride present in synthetic or bone apatite enhances osteoblastic activity [3, 4]. In vitro studies also showed that fluoride-containing apatite inhbited osteoclastic activity [5].The aim of this study was to com pare the biocompatibility and biodegradation carbonateand fluoride-containing apatites implanted in dog mandible bone. Materials and Methods Carbonate hydroxyapatite (CHA), carbonateand fluoride-containing apati te (CFA) and carbonateand fluoride-free apatite (HAP) were synthesized according to me hods previously described [6, 7]. Their chemical and crystallographic properties were determined us ing X-ray diffraction (XRD), FTIR, thermogravimetry (TG-DTA), and AAS. The materials were pow dered, sieved with 200-mesh, sterilized and implanted in surgically created holes (3mm diamet er) in the mandible of Beagle dogs. The implanted materials were covered with biodegradable membranes to prevent material loss during the experiment. After 2, 3, 4, 5, and 6 weeks, the dogs were sacrif iced under anesthesia. Histological stained sections of the mandible bones were observed using a microscope. Results XRD analysis confirmed the substitution of carbonate (CO 3) and fluoride (F) in the apatite structure based on shifts in diffraction peaks reflecting lattice paramete r changes due to CO 3-for-PO4 and Ffor-OH substitutions in calcium hydroxyapatite, Ca 10(PO4)6(OH)2. Carbonate substitution in CHA and in CFA was demonstrated as the absorbance bands at about 1400 to 1560 and at about 770 to 800 cm-1 in the FT-IR spectra 7 nd the weight losses above 400 C in TG-DTA. Histological sections of these materials showed a clear diffe renc in the extent of resorption or dissolution of the implanted apatites and in the pattern and type of bone f ormation. HAP remained Key Engineering Materials Online: 2003-05-15 ISSN: 1662-9795, Vols. 240-242, pp 395-398 doi:10.4028/www.scientific.net/KEM.240-242.395

Thermal Stability of Mineralized and Demineralized Dentin: A Differential Scanning Calorimetric Study

The purpose of this study was to determine the difference, if any, in the thermal stability of collagen in mineralized and demineralized dentine compared to that in unmineralized tissues, using differential scanning calorimetry, DSC. Human tooth dentin blocks, about 1 x 1 x 2 mm in size, were used in this study. Some dentin blocks were demineralized using a Plank Rychlo solution; others, using EDTA solution. The mineralized dentin showed an exothermic peak at about 310 degrees C and the combustion of organic materials was completed at about 450 degrees C. For the demineralized dentin, the combustion was completed at higher temperature range and showed a strong exothermic peak at about 470 degrees C. An exotherm at the temperature between 450 degrees C and 470 degrees C was also observed in DSC pattern of native type I collagen from calf skin and rat tail tendon. DSC pattern of rat tail collagen showed a close similarity to that of the demineralized dentin. Statistically, the same heat flow value was obtained both from the mineralized dentin and the demineralized dentin and from the native type I collagen. These findings indicated that the thermal stability of collagen in dentin is lower than collagen in uncalcified connective tissue. It is suggested that in calcified collagen, the apatite crystallites may have intruded into spaces of the crosslinks of intra- and inter-fibrils, and in so doing, destroyed the crosslinks.

Mode of Occurrence of Brushite and Whitlockite in a Sialolith

A micro-focus X-ray diffractometer was applied to a ground section of sialolith, and localization of brushite and whitlockite was found. The sialolith was composed of a central core of organic material and a layered cortex of mineral components. The major component of the mineral cortex is apatite. Brushite and whitlockite locate independently at the surface layer of the cortex.

Variations in Dental Enamel Crystallites and Micro-Structure

Abstract Dental enamel crystallites consist of relatively highly crystalline biological apatite, which include a large amount of carbonate ions in the apatite crystal lattice. However, this common understanding was achieved only after a great deal of research because of the wide variation in the chemical composition of dental enamel. In this paper, the difference between biological and mineral apatite is briefly reviewed, and how to obtain information easily concerning the chemical composition of dental enamel, which is a major factor in determining the physical-chemical properties, using non-destructive high-accuracy analytical instruments, such as FT-IR spectrometry, FT-Raman spectrometry and X-ray diffraction. Variations in the enamel structure observed by instruments other than optical or electron microscopes were not reported in relation to tooth type differences. These variations are referred to herein as variations in enamel microstructure, such as micro-pores. Finally, a number of problems with respect to variations in dental enamel that cannot be ignored when treating dental enamel are discussed.

Calcification and Crystallization in Bovine Enamel

The degree of crystallinity of the inorganic components in bovine enamel during maturation was calculated and was compared with the degree of calcification. The process of calcification was quantified using monochromatic X-ray microradiography, and the extent of crystallization was analyzed using an X-ray microdiffraction method. The results showed two notable phenomena: (1) that calcification continued for a short time after the eruption of the tooth, and (2) that the crystallization of the inorganic components was delayed in relation to the process of calcification before eruption, but caught up and progressed rapidly after eruption.

Electron microscopy of octacalcium phosphate in the dental calculus.

The purpose of this study was to morphologically demonstrate the presence of octacalcium phosphate in the dental calculus by judging from the crystal lattice image and its rapid transformation into apatite crystal, as part of our serial studies on biomineral products. We also aimed to confirm whether the physical properties of octacalcium phosphate are identical with those of the central dark lines observed in crystals of ordinary calcifying hard tissues. Electron micrographs showed that crystals of various sizes form in the dental calculus. The formation of each crystal seemed to be closely associated with the organic substance, possibly originating from degenerated microorganisms at the calcification front. Many crystals had an 8.2-A lattice interval, similar to that of an apatite crystal. Furthermore, some crystals clearly revealed an 18.7-A lattice interval and were vulnerable to electron bombardment. After electron beam exposure, this lattice interval was quickly altered to about half (i.e. 8.2 A), indicating structural conversion. Consequently, a number of apatite crystals in the dental calculus are possibly created by a conversion mechanism involving an octacalcium phosphate intermediate. However, we also concluded that the calcification process in the dental calculus is not similar to that of ordinary calcifying hard tissues.

Early Tissue Response to Modified Implant Surfaces Using Back Scattered Imaging

Purpose:It is now well known that implant surface properties affect osseointegration. Grit-blasting with abrasives and coating by plasma are methods to modify implant surfaces. This study aimed to compare the direction of new bone formation associated with three types of surfaces. Materials and Methods:Titanium (Ti) alloy rods grit-blasted with alumina abrasive (Group 1, G1), with apatitic abrasive (Group 2, G2), and with apatitic abrasive and plasma-sprayed with hydroxyapatite (Group 3, G3) were implanted in surgically created defects in tibias of New Zealand white rabbits for 2 and 4 weeks. After sacrifice, the implants and surrounding bones were obtained and analyzed using back scattered imaging. Results:Differences in patterns of bone formation among the groups were observed: originating from the cortical bone towards the implant surface (Type A), surrounding the implant (Type B) and originating from the medullary cavity (Type C). G1 and G3 showed Types A and B while G2 exhibited Types A, B and C. After 4 weeks, greater amount of new bone was observed in G2 group compared with those in G1 and G3 groups. Conclusions:This study demonstrated that patterns of bone formation are influenced by methods of surface modification.

Weddellite in Submandibular Gland Calculus

Scanning electron microscopy of a submandibular sialolith showed octahedral and dipyramidal crystals located at the surface layer of cortex. The crystal habits observed were consistent with those of a tetragonal crystal system. X-ray microcdiffraction revealed the presence of weddellite. The origin of weddellite within the calculus remains to be determined.